Fluid power transmission



2 Sheets-Sheet 1 Filed July 25, 1956 u. wmiamwmzmi 9m OON OOQ

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PISS ALISOOSIA INVENTORS. FRANKLIN VEATCH a ERNEST C. MILBERGER United States Patent FLUID POWER TRANSMISSION Franklin Veatch, Cleveland, and Ernest C. Milberger, Maple Heights, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio Filed July 25, 1956, Ser. No. 600,023

3 Claims. (Cl. 252-75) This invention relates to fluid power transmission and to a power transmission fluid characterized by an ASTM slope below 0.3, comprising a light mineral oil of normal viscosity index, and an inorganic gelling agent and aliphatic amine in amounts to impart an ASTM slope of below 0.3 to the mineral oil.

Petroleum oils have certain performance characteristics which make them particularly suitable for use as power transmission fluids. A power transmission fluid which is well suited for the job for which it is intended must have good flowability and pumpability, lubricating ability, chemical stability, rust-inhibiting ability, demulsibility, and defoaming ability. All of these characteristics are important, and should be displayed over the entire range of temperatures at which the system is to be used. All fluids, however, undergo a change in viscosity with temperature. The rate of change of viscosity with change in temperature which characterizes petroleum oils is not as low as that for many synthetic oils such as silicone oils and the Ucon oils, which are polypropylene glycol ethers, and this is a disadvantage.

The rate of change in viscosity with temperature of petroleum oils ordinarily is measured by the viscosity index, usually abbreviated V.I. The higher the V.I., the lower the rate of change in viscosity, and the better the petroleum oil for use as a hydraulic fluid. However, the viscosity index loses its sensitivity as a characterizing property when the oil has an exceptionally low rate of change in viscosity, of the order of that which characteriz es many synthetic oils. A viscosity temperature relationship has been'developed which is superior to the viscosity index for this type of petroleum oil. This is the ASTM slope, adopted as a standard method by the American Petroleum Institute, Standard 533-43, ASTM designation D341-43. This slope is the tangent of the acute angle of the viscosity-temperature plot of the oil on the ASTM standard chart D-341-43. The smaller the ASTM slope, the flatter the curve, and the lower the change in viscosity with temperature.

Typical ASTM slopes of a number of petroleum and synthetic oils are given below:

Monohutyl poly 1,2-oxy propylene glyeols. See Kirkpatrick U.S. No. 2,615,853.

The lighter mineral oils of low viscosity would be especially suitable for use as power transmission media because of their low sludge and deposit-forming tendencies compared to the heavier oils. However, light oils lack lubricating ability under operating conditions, and ASTM slope is in most instances too high. In fact, the light oils have such a low viscosity at high temperatures that they are not suited without modification for such purposes.

in accordance with this invention, power transmission fluids are provided having a viscosity within the range from to 1000 SSU at F. and from .50 to 750 SSU at 210 F., and an ASTM slope below about 0.3, employing as the base oil light lubricating oils having a viscosity of about 50 to 300 SSU at 100 F. and from 25 to 55 SSU at 210 F. The ASTM slope of the light lubricating oils is not critical because the power transmission fluids of the invention nonetheless have an ASTM slope of less than 0.3, considerably less than many synthetic oils and most ordinary petroleum hydrocarbon oils, even when highly refined, as the above table shows.

The power transmission fluids of the invention comprise from 1 to 3% based on the weight of the oil of an inorganic gelling agent, and from about 1% to about 60% by weight of the gelling agent of an aliphatic amine having an aliphatic radical from 8 to 20 carbon atoms. These two additives in combination increase the viscosity of the light oil to the point where the composition has a viscosity suitable for a power transmission fluid, and in addition improve the ASTM slope of the base oil to below 0.3. The compositions of the invention are fluid under all conditions of use at normal and elevated temperatures.

These eflects are not obtained in the absence of either the inorganic gelling agent or the aliphatic amine. The increase in the viscosity and decrease in the ASTM slope due to the. inorganic gelling agent are relatively small. The aliphatic amine alone has no efllect upon viscosity or ASTM slope. However, in the presence of the inorganic gelling agent the aliphatic amine eiTects a further increase in viscosity, and a further decrease in the ASTM slope. Thus, the amine makes it possible to achieve higher viscosities and lower ASTM slope within the desired ranges, using lesser amounts of the inorganic gelling agent. The viscosity-increasing and ASTM slope decreasing effects of the amine are obtained after the mixture of oils, gelling agent and amine has been heated to temperatures of 300 F. or higher.

The lubricating oil stock used in preparing the compositions of the invention will have a viscosity within the range from 50 to 300 SSU at 100 F. and 25 to 55 SSU at 210 F. The base stock is preferably a lubricating oil fraction of petroleum and it may be unrefined, acidrefined or solvent-refined, as required for the particular lubrlcating need. The nature of the base oil makes little difierence in the relative consistencies of the compositions, although conventionally acid-refined oils produce slightly thicker fluids than the solvent-refined oils. The viscosity index of the oil is not critical.

The inorganic gelling agent can be any inorganic material which is dispersible in the oil and which is so finely divided as to be nonabrasive. The preferred materials are the aerogels which can be formed from any material not incompatible with the oil, such as silica, alumina and magnesia. Other gel-forming metal oxides, hydroxides and sulfides can be used, of which attapulgite, the bentonites (such as Wyoming bentonite, montmorillonites and hectorite), beidellite, saponite, nontronite, sepiolite, biotite, vermiculite and zeolites, synthetic clays such as magnesia-silica-sodium oxide, lime-silica-potassium oxide and baria-silica-lithium oxide are exemplary, as well as synthetic zeolites, of which the complex aluminum silicates are exemplary.

A series of silica aerogels which can be used as the inorganic gelling agent of the invention are manufactured by Monsanto and marketed under the trade name Santocelf Santocel C is prepared from an alkali silicate solution. Silicic acid dissolved in caustic alkali such as sodium hydroxide and the alkali silicates, such as sodium silicate, can be obtained from various natural minerals and clays or by fusing silicon dioxide with alkali hy droxides or carbonates. Fused alkali silicates such as water-glass, sodium tetra-silicate (Na Si O can be completely dissolved on long heating with water, but the result is not a solution of the silicate as such but of silicic acid peptized by alkali as well as free alkali. By addition of an acid to such a solution, for example, an inorganic acid such as sulphuric acid, hydrochloric acid or carbonic acid, or an organic acid such as acetic acid, oxalic acid or formic acid, the silicic acid is precipitated in the form of a gel'which is called a hydrogel or aquogel. The structure of this gelhas not been fully elucidated but it is generally accepted that it is composed of a honeycombstructure of the silicon dioxide SiO within the pores of which is enclosed the aqueous solution remaining after precipitation of the silicic acid. Thus, it can be generally stated that these hydrogels can be obtained starting from'any water-soluble alkali silicate, including not only water glass as mentioned above but sodium metasilicate Na SiO sodium metasilicate nonahydrate Na SiO 9H O and sodium disilicate Na Si O All of these silicates are soluble in' water, in which they decompose to "form silicic acid solution.

Suchan aqueous solution of silicic acid will contain sufficientSiOg in'solution to form a hydr'ogel' containing within the rangefrom 3% to about 12% silica as SiQ after gel formation by addition of the acid. The amount of silica can readily be calculated, depending upon theamount of'acidwhich is required toacidify are solution and whether the acid employed is concentrated or diluted. his not necessary to characterize'the silicic acid solution in terms of the alkali content calculated either as Na O or NaOH inasmuch as this forms a salt with the anion of the acid employed and is washedout of the aquogelat the time of alcogel formation.

After formation of the aquogel, the gel is washed free from salts and excess acid,-and then converted to an alcogel by soaking ineth-yl' alcohol or some other watersoluble volatile aliphatic alcohol. Several portions'of the alcohol may be necessary completely'to remove the aqueous solution. The res'ulting'alcogel then is placed'in an autoclave. In order to remove the liquid phase without-a collapse of the gel structure, the autoclave is heated ata temper'ature'above the critical temperature of'the alcohol, and the pressure is allowed to increase to a point above the critical pressure of the alcohol. The vent valve is then opened and the alcohol allowed to escape. Under these conditionsthe silica gel structure remains practically undisturbed and the liquid phase of the gel is replaced with air. The material is then reduced in particle size by blowing it through a series of pipes containing sharp bends with jets of compressed air. Santocel C has a secondary particle size of about three to five microns. r

Santocel A is prepared as set forth for Santocel C up to the point of removal of the product from the autoclave. This material is run through a continuous heating chamber where it is heated for one-half hourto a temperature of about 1500 F. toeliminate the last traces of volatile material. It is then broken down in a reductionizer or micronizer to a particle size of about one-sixteenth'inch in diameter. The SiO content of the originalhydrogel used in preparing Santocel C is approximately-995%, whereas that of Santocel A is about 7.0% AR is a modification of A, difiering only in that th material is reductionized to about the same particle size as C, approximately three to five microns in diameter.

ARD is a modification of AR, differing only in that ARD is densified by extracting air under vacuum, "and therefore has a smaller volume than AR.

AX is an A which has not been devolatilized.

CD is a C which has been devolatilized as set forth for Santocel A. The Santocel is reductionized before being devolatilized. l

CD R differs slightly from CD in that-the CD R has been devolatilized just' afterheating in the autoclave and then reductionized." It differs from CD in that the latter is reductionized before being devolatilized.

The primary 'differences between the A and C series are as follows: a

AR 0.029 ARD I 0.056 to 0.064 c e 0.082

i In general, AR and ARD show superior gelling ability and the As in general are better than the Cs.' Silica aerogels which have been devolatilized generally have a higher gelling'efiiciency than the undevolatilized aerogels. -Other types of inorganic gelling agents which'may be used includea Furned Silica marketed by B. F, Goodrich Company. It is finely divided and appears very much likean aerogels It is made by a combustion orvaporization process, as asource of white carbon blackfgfgr the-rubber industry; {The particles are several micronsrin size-and-porous-in naturcv Another materialis Linde Silica Flouriimarketedby Linde Air Products Co. It 'is very similar in physical appearance to the silica'aerogel. The particle size ofthe silica is purported to be 0.01 to 0.05 micron and the silica is said to be manufactured by burning silicon tetrachloride and'collecting the combustion product on cool plates analogous to the production of carbon black. The part-iclesare thought to be'a ggregates or-clusters of particles rather than of sponge-like'character.

' Still-another inorganic gelling agent known'is Ludox silica'from du Pont, which is "known asa silica sokand silica derivatives thereof It has aparticle size of-tlie order of"0.0l to 0.03 micron. i i A Ihe-"silicas from Columbia-Southern also are useful. These have the following properties.

Brunauer-Emmett- Wet Screen Retained 325 Mesh, Percent Teller Nitrogen Absorption Surface Area, mJ/gm.

0.004 257. 0 0 m 236. 5 0.02. ca. 210. 0 0.008. 215. 5 0.004 228.0

Any aliphatic saturated and unsaturated primary and secondary amine can be used. Those having aliphatic radicals of from eight to twenty carbon atoms are the most satisfactory. The primary amines will have one such radical, and the secondary amines two. The primary aliphatic amines are preferred. Typical are octylamine, decylamine, dodecylamine, stearylamine, palmitylamine, myristylamine, oleylamine, myricylamine, dioctylamine, methyl decylamine, octyl dodecylamine, butyl stearylamine, distearylamine, dilaurylamine, ethylnonylamine and dieicosylamine. Decylamine and dodecylamine are illustrated in the examples, but it will be understood that any member of this class of amines can be substituted therefor with satisfactory results.

The amine should not be volatile at the temperatures at which the lubricant is to be used, and accordingly usually has a boiling point above about 300 F. The amine should also be oil-dispersible or oil-soluble and will also be hydrophobic if it has a sufficiently long-chain aliphatic group, over about ten to twelve carbon atoms.

The relative proportions of the inorganic gelling agent and the oil will vary somewhat depending upon the desired viscosity in the final compositions, and the viscosity of the oil used. Compositions made with the lower viscosity oils require a somewhat larger amount of inorganic gelling agent to give a composition of the same viscosity. .The compositions of the invention are fluid at 100 F. or below. In general, the amount of inorganic gelling agent falls within the range of from 1 to 3% and in most cases preferably would be from 2 to 3%.

The viscosity, as might be expected, increases in a fairly linear relationship with increase in concentration of the inorganic gelling agent and the amount of gelling agent can be selected in relation to the desired viscosity in view of this.

The concentration of the amine will usually lie Within the range from about 1% to about 60%, based on the weight of the inorganic gelling agent, but here again the amount employed will depend upon the increase in viscosity desired, the amount and nature of the gelling agent and the economics involved. Amounts in excess of 60% tend to increase viscosity much less than smaller amounts (cf. Example 8) and therefore more than 60% would not be used. A cheaper compound can of course be used in much larger quantities than an expensive compound at the same total cost of the composition.

The composition is made simply by mixing the inorganic gelling agent, the oil and the aliphatic amine in any order or manner. The amine also can be incorporated with the inorganic gelling agent before mixing with the oil, for example, by dissolving the amine in a solvent such as pentane, mixing it with the gelling agent and then evaporating the pentane. Such a treating agent can be sold as an article of commerce and dispersed in an oil when the composition of the invention is to be prepared.

Generally, the amine is dispersed in the oil and the inorganic gelling agent added thereto and mixed there- 'with. Any simple mixing technique can be employed and if desired the mixture can be homogenized in a colloid mill or subjected to high shear by ejection or atomization through a small orifice such as a diesel injector nozzle, although this is unnecessary.

The amine must be uniformly distributed in the composition or on the inorganic gelling agent and for this reason the amine is oil-dispersible or oil-soluble or else soluble in some medium in which it can be applied to the gelling agent before incorporating the latter in the oil.

After the amine, inorganic gelling agent and oil have been mixed, the composition is heated to at least 300 F. This develops the thickening effect of the amine. Heating to this temperature while subjecting the composition to high shear is sufiicient to develop the effect, but a pro longed heating at a temperature above 300 F., say from a few minutes to a few hours, does no harm provided the temperature is not so high as to result in decomposition of any component of the mixture.

The composition of the invention is not limited to the oil, gelling agent and amine. Any of the materials conventionally added to lubricants can be included. The expression consisting essentially of as used herein is intended to refer to the components which are essential to the composition, that is, the oil, the inorganic gelling agent and the amine, and the expression does not exclude other components from the composition which do not render it unsuitable as a hydraulic fluid.

The following examples illustrate preferred embodiments of the invention:

EXAMPLES 1 TO 8 Into 87.2 g. of straw paraflin oil (API gravity at 60 F. 31.4, viscosity at F. 74.1 SSU, at 210 F. 36.6 SSU, ASTM slope=0.78, viscosity index='66) was mixed 0.087 g. of Armeen 10-D (commercial grade decylamine). Into this mixture was stirred 0.87 g. of Santocel AR silica aerogel. The mixture was homogenized and heated to 350 F. with constant stirring.

A second composition was prepared using 1.74 g. of the Santocel.

In each of these compositions 0.1% amine by weight of the composition (10% by weight of the silica aerogel) was employed. A second group of three compositions was prepared in which the amount of amine was increased to 50% by weight of the silica aerogel, and a third group in which the amount of amine was 100%.

The viscosities of each of these compositions were determined in an Ubbelohde capillary tube viscometer at 100 F. The results were as follows:

For purposes of comparison there are included in the table the viscosity of the straw parafiin oil without Santocel AR and without amine (Control) and the viscosity of oil compositions containing 1 and 2% silica aerogel by weight of the oil but no amine (Examples 1 and 5).

Table I Percent De Percent cyclamine Viscosity Example No. Silica by wgt. of (SSU at Aerogel silica 100 F.) aerogel None None 74. 1

1 None 91. 2

2 None 217.6

The data shows that marked increase in viscosity resulted upon addition of the amine in each instance. The greater the silica aerogel concentration, the greater the efiect of the amine on viscosity.

EXAMPLES 9 AND 10 Two compositions were prepared containing 2.5% Santocel AR. One of these compositions contained 0.25% Armeen 10-D and the other did not contain amine. Into 87.2 g. of straw parafiin oil having the same properties as the oil of Examples 1 to 8 was mixed 2.18 g. of Santocel AR. The second composition was prepared by mixing 0.218 g. of Armeen 10D with the oil and then mixing in 2.18 g. of Santocel AR.

Each of the compositions was subjected to high shear by recycling through a small gear pump and through a steel coil at 400' C. in a furnace. After this treatment they were subjected to further shearing by ejection or atomization through a diesel injector nozzle set at 2500 to 3000 p.s.i.g. Oil was ejected from the nozzle into a flask and was held in a partial vacuum for a short time to remove and entrain 7 Theviscosity of each composition was determined 'in a Stormer viscometer and compared with'th'e viscosity of thestra'w paraflin oil.

T abl 11 Percent Percent Deeylam'ine Viscosity ASTM Example No. Silica: i. by wgt'. o! '(SSUiat Slope I Aerogel silica .100 F.) aero'gel Nbiie 'Nime" 7s his 2.5 None 270' The sample containing 0.25% decylamine had a higher viscosity than the sample without amine, and a considerably lower ASTM slope than therbase oil. The ASTM slope of the oil of Example 10 was 0.09, compared to 0.78 for the base oil. The curves from which the ASTM slope is calculated are shown in Figure 1. The decrease in ASTM slope compared to the straw paraffin oil is noteworthy. The oil of Example 10 actually has a lower AST M slope than a 133 V1. oil, included for comparison, Whose ASTM slope is 0.66.

' EXAMPLE 1;

A composition wasprepared having the following for: mula-tion:

Percent Solvent-extractedneutral oil (250 SSU at 100,? E.) 96. 0 Santocel AR silica aerogel 3.0

Armeen 1 2D (commercial grade dodecylarnine) 0.5 Paratac (an isobutylene polymer commercially used compounding greases} L 0.5

The data'shows'the improvement in viscosity gained by incorporating both silica aerogel and the amine "iii tl1e on; M The curves from which the ASTM slope is calculated are shown in Figure 2. The oil of Example II has a lower ASTMf slope than the solvent-extraeted neutral oil.

'All percentages in the specification and "claims are by weight; Amounts of the amine are by weight (if-the inorganic gelling agent, unless otherwise indicated; Amounts of the inorganic gelling agent are-by weight of the oil.

" We claim:

1'. In'a process for fluid power transmission, the improvement which comprises transmitting power by means of a fluid having a viscosity within "the range from "75 to 1000 SSU at 100 Fjand fr'om to 750 S SU at 210 F.,and having an AsTM-slo'pebelow' about 0.3, consisting essentiallyof amineral lubricating oil having a viscosity within the rangefrom 50 to 300' SSU at 100 F; and from 25 to SSU at'2l0-' F., a silica aerogel in an amount within the range from 1 to 3% imparting an increased viscosity and a decreased ASTM slope to the oil and an aliphatic amine having from about 8 to about 20 carbon atoms in an amount within the range from'about 1 to about by weight of the silica aerogel, imparting a further increase in'viscosity and a further decrease in ASTM slope supplementing the effect of the silica aerogel.

'2. A process in accordance with claim 1 in which the aliphatic amine is a primary amine having from about 8 toabout 20 carbon atoms.

3.'A process in accordance with claim v1 in which the amine is dodecylamine.- i

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR FLUID POWER TRANSMISSION, THE IMPROVEMENT WHICH COMPRISES TRANSMITTING POWER BY MEANS OF A FLUID HAVING A VISCOSITY WITHIN THE RANGE FROM 75 TO 1000 SSU TO 100*F. AND FROM 50 TO 750 SSU AT 210*F., AND HAVING AN ASTM SLOPE BELOW ABOUT 0.3, CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL HAVING A VISCOSITY WITHIN THE RANGE FROM 50 TO 300 SSU AT 100*F. AND FROM 25 TO 55 SSU AT 210*F., A SILICA AEROGEL IN AN AMOUNT WHICH THE RANGE FROM 1 TO 3% IMPARTING AN INCREASED VISCOSITY AND A DECREASED ASTM SLOP TO THE OIL AND AN ALIPHATIC AMINE HAVING FROM ABOUT 8 TO ABOUT 20 CARBON ATOMS IN AN AMOUNT WITHIN THE RANGE FROM ABOUT 1 TO ABOUT 60% BY WEIGHT OF THE SILICA AEROGEL, IMPARTING A FURTHER INCREASED IN VISCOSITY AND A FURTHER DECREASE IN ASTM SLOPE SUPPLEMENTING THE EFFECT OF THE SILICA AEROGEL. 